Probleme mit iChat auf G5

[le-dude]

Hallo Gemeinde,

seit einiger Zeit macht iChat Probleme auf meinem iMac G5 Probleme.
Genauer: es geht gar nichts mehr.
Fehlermeldung: der Gesprächspartner antwortet nicht.
Meine Chat-Partner melden die Fehlermeldung: ungültige IP-Adresse.

Etwa genauer:

iChat Connection Log:
2008-12-22 21:52:49 +0100: AVChat started with ID 1438317989.
2008-12-22 21:52:49 +0100: derchirdude3: State change from AVChatNoState to AVChatStateWaiting.
2008-12-22 21:52:50 +0100: 0x9a66170: State change from AVChatNoState to AVChatStateInvited.
2008-12-22 21:52:57 +0100: 0x9a66170: State change from AVChatStateInvited to AVChatStateConnecting.
2008-12-22 21:52:57 +0100: derchirdude3: State change from AVChatStateWaiting to AVChatStateConnecting.
2008-12-22 21:53:24 +0100: 0x9a66170: State change from AVChatStateConnecting to AVChatStateEnded.
2008-12-22 21:53:24 +0100: 0x9a66170: Error -8 (Did not receive a response from 0x9a66170.)
2008-12-22 21:53:24 +0100: derchirdude3: State change from AVChatStateConnecting to AVChatStateEnded.
2008-12-22 21:53:24 +0100: derchirdude3: Error -8 (Did not receive a response from 0x9a66170.)

Video Conference Error Report:
52.351615 @SIP/SIP.c:2719 type=4 (900A0015/0)
[SIPConnectIPPort failed]
[]
54.362277 @SIP/SIP.c:2719 type=4 (900A0015/0)
[SIPConnectIPPort failed]
[]
56.365142 @SIP/SIP.c:2719 type=4 (900A0015/0)
[SIPConnectIPPort failed]
[]
58.367065 @SIP/SIP.c:2719 type=4 (900A0015/0)
[SIPConnectIPPort failed]
[]
60.369523 @SIP/SIP.c:2719 type=4 (900A0015/0)
[SIPConnectIPPort failed]
[]

Habt Ihr eine Idee, wo das problem liegt?
Soll ich Leo neu installieren?
Danke,

R.